Process for the preparation of polyurethane rigid foams having a low thermal conductivity and their use

ABSTRACT

The invention relates to a process for preparation of rigid polyurethane foams having low thermal conductivity by reacting 
 
  a) organic and/or modified organic polyisocyanates with 
  b) at least one relatively high molecular weight compound having at least two reactive hydrogen atoms and optionally 
  c) low molecular weight chain extenders and/or crosslinking agents in the presence of 
  d) cyclopentane (d1) or mixtures (d2) which contain: 
 
  d2i) cyclopentane and/or cyclohexane and 
  d2ii) at least one compound which is homogeneously miscible with cyclopentane and/or cyclohexane and preferably has a boiling point below 35 DEG C, selected from the group consisting of the alkanes, cycloalkanes having not more than 4 carbon atoms, dialkyl ethers, cycloalkylene ethers and fluoroalkanes,
 optionally in conjunction with water, as blowing agents (d), 
 
  e) catalysts and optionally 
  f) auxiliaries and/or additives. 
 
&lt;??&gt;The rigid polyurethane foams are used in the refrigerator industry and as insulating material in heating and composite elements.



